The present invention relates to a controlled heating unit for extracting solvent from sludge by distillation, in particular for dry-cleaning machines.
It is known that significant amounts of perchloroethylene are absorbed by the filtration powders during the operating cycle of dry-cleaning machines.
In order to recover the perchloroethylene from the powders, it is known to subject said powders to distillation, but the efficiency of conventional systems leaves solvent residuals in the powders in amounts in the range of even more than 10%.
It is also known that since the solvent does not evaporate at temperatures below 120 degrees and it degrades at temperatures above 150 degrees, the sludge must be heated at temperatures comprised between said two values.
The sludge to be treated also contains other residuals of the washing operation, and the solvent content is such that restrictive laws make the storage and disposal of the solvent residuals not only expensive but sometimes impossible.
The interest in developing a new distillation process which can reduce the perchloroethylene content to such a level as to allow the operator of the washing system to contract companies specialized in the treatment of distillation waste is evident.